International Patent Application Publication Number WO 2008/010921 and International Patent Application Publication Number WO 2008/103949 disclose certain compounds that are reported to be useful to modify the pharmacokinetics of a co-administered drug, e.g. by inhibiting cytochrome P450 monooxygenase. One specific compound identified therein is a compound of the following formula I:

There is currently a need for improved synthetic methods and intermediates that can be used to prepare the compound of formula I and its salts. There is also a need for improved methods for preparing intermediate compounds that can be used to prepare the compound of formula I and its salts. The improved methods and intermediates may reduce the cost, time, and/or the amount of waste associated with the existing methods for preparing the compound of formula I and its salts.